The foreign institutional investors (FIIs) were net buyers to the tune of Rs 1,266.62 crore in the futures & option segment on Tuesday.According to data released on the NSE website, FIIs were net buyers of index futures to the tune of Rs 351.18 crore and they bought index options worth Rs 86.46 crore. They were net buyers of stock futures to the tune of Rs 829.36 crore while they sold stock options worth Rs 0.39 crore.As per data available on the Sebi website - FIIs were net sellers of stocks worth Rs 929.80 crore in the spot market on Monday. Domestic mutual funds (MFs) were net buyers of shares worth Rs 402.74 crore on the same day.